There is a continuing need for flexible hoses for the safe transmission of fluids in industry. Of particular need is a rough service flexible hose that can withstand the high pressure transmission of corrosive fluids, yet is resistant to chafing, wearing and crushing forces which are endemic in the rough service work place.
Extruded convoluted plastic hoses have been developed by industry as flexible means for the transmission of corrosive fluids and are commercially available in a variety of plastic materials including highly resistant materials such as polytetrafluoroethylene (Teflon) and the like. In one configuration, the convolutions are arranged as disconnected annular valleys which separately encircle the perimeter of the hose along its length and have mating adjacent annular valleys along its interior passageway to resist collapse of the passageway. Such configuration provides flexibility and some resistance to collapse of the hose but is generally seen as not suitable for rough service in that flexing tends to create breaks in the hose and the internal valleys tend to collect fluid which resists drainage from the internal passageway.
In another configuration, hoses are formed such that the exterior of the hose comprises a continuous valley configured as an endless spiral through the length of the hose, with the interior passageway of the hose comprising an adjacent mating spiral valley through its length. Such convolution provides structural integrity to the passageway of the hose in that it tends to resist collapse of the passageway and the interior spiral promotes drainage of the passageway. Such hose is still not generally seen as suitable for high pressure and/or vacuum use in a rough service environment in that its ability to resist collapse and rough service treatment in the work place is not great.
U.S. Pat. Nos. 4,196,031 and 4,342,612 disclose improved extruded spiral convoluted plastic hose wherein a wire spring, formed to a spiral, is wrapped around the hose within the exterior valley, sized so that the spring snaps into the exterior valley of the convoluted hose and is captured by the sides of the valley of the plastic hose in an arrangement where the wire nests the hose to resist collapse of plastic hose. The wire is preformed and stressed to maintain a helical form generally conforming to the helix of the extruded spiral plastic hose. The valley and the wire are sized so that the walls of the valley resist release of the spring once it is snapped in and thus the spring supports the plastic hose from internal collapse.
In order to apply the wire to the extruded hose, the patents disclose a method wherein wire is preformed to a helical diameter smaller than the spiral of the plastic hose and mounted to rotate around the preformed hose as the hose progresses from an extruding head through a wire wrapping station. Thus, the hose is moved longitudinally through a point and wire is applied without supporting the passageway from collapse. Such method requires close tolerances to assure the nesting of the wire in the valley without collapse and/or damage to the hose and particularly critical tolerances when the hose is heated or otherwise softened to provide a nested effect by the walls of the valley as disclosed in the patents. To avoid chafing of the wire against the extruded plastic hose, the patents describe laying a 0.010 inch fiber glass interleaving tape in the crotch of the valley positioned between the spring and the hose.
Such hose of the above patents are said to provide some improvement in resistance to vacuum collapse of a preformed spiral hose. It appears that the improvement is in large part dependent upon the effectiveness of the capture of the wire by adjacent sides of a valley and thus the ability to hold close tolerances in the application of the wire and/or the degree of other means which might be used to envelope or otherwise resist outward movement of the wire from the valley and/or inward movement of the plastic from the wire.
Such hose as disclosed in the patents provide little if any improved resistance to burst under high pressure fluid flow, in that the captured nesting within the valley appears to preclude support to peeks between valleys and damage caused by the wire chafing the hose within the valley is problematic in reducing resistance to bursting.
It is an object of the present invention to provide a composite, preformed hose having improved resistance to high fluid pressures.
It is a further object of this invention to provide a composite, preformed hose having resistance to crushing and abrasion.
It is a further object of the present invention to provide a method and apparatus for the manufacture of composite preformed hose.
These and other objects of the invention will be apparent from the following.